Casting of magnesium



Patented Jan. 5, 1937 UNl'lED STATES CASTING F MAGNESIUM Fritz Hansgirg,Itadenthein, Austria, assignor to American Magnesium Metals Corporation,Pittsburgh, Pa., a. corporation of Delaware No Drawing.

Application November 21, 1934,

Serial No. 754,176. In Austria April 25, 1934 9 Claims.

This invention relates to the casting of mag- Y nesium and alloys richin magnesium. I use the term magnesium in the following description andin the appended claims to mean both magnesium metal and also alloys ofthe said nature.

The main objects of my invention are to provide a casting method inwhich the metal is protected against oxidation during casting and. in

which there is produced on the casting a coating 1 of a nature toprevent the metal cast from tarnishing.

According to the present invention the surface of the magnesium to becast is brought, during casting, in contact with sulphides of antimony15 or bismuth. In this manner castings are obtained which are free frompitting and exhibit a smooth surface. Moreover, by superficial alloyingof the magnesium with the antimony or hismuth a coating is formed on thecasting which 20 prevents the metal cast from tarnishing.

The method is suitable for the casting of magnesium in temporary andpermanent molds of every kind. The antimony or bismuth compounds can bedusted in the solid state upon the 25 surface of the mold, or can besprayed or painted on in the form of a suspension in an aqueous or nonaqueous dispersion medium. When casting in temporary molds (sand moldsor molds of other material) the compounds can either be applied to thesurface of the mold in the specified manner in the form of a blackwashor incorporated in the loose molding material, or used in both ways. Ihave found for example that an addition of 2-10 parts by weight ofantimony pentasulphide,

35 referred to the total quantityof molding material used, is verysuccessful for the purpose in view.

I claim:

1. That method of casting magnesium which comprises incorporating in themold a salt selected from the group consisting of sulfides of antimonyand bismuth, and casting magnesium in said mold and thereby minimizingburning of the metal during casting and effecting alloying 45 of thesurface layers of the casting with the metal of said sulfide whereby thecasting is provided with a protective coating.

2. That method of casting magnesium which comprises mixing the moldingmaterial intimate- 50 1y with a salt selected from the group consistingof sulfides of antimony and bismuth, and casting magnesium in a moldmade of said molding material and thereby minimizing burning of themetal during casting and effecting alloying of the surface layers of thecasting with the metal of said sulfide whereby the casting is providedwith a protective coating.

3. That process of making amagnesiumcasting which comprises pouring themolten metal so into a mold the molding material of which contains, atleast for the parts of the mold adjacent to the cast metal, a saltselected from the group consisting of sulfides of antimony and bismuth,minimizing thereby burning of the metal during casting and effectingalloying of the surface layers of the casting with the metal of saidsulfide to provide the casting with a protective coating.

4. A method of treating the surface of a mold part for castingmagnesium, which comprises applying to the surface of such mold part asalt selected from the group consisting of sulfides of antimony andbismuth, minimizing thereby burning of the metal during casting andeffecting alloying of the surface layers of the casting with the metalof said sulfide to provide the casting with a protective coating.

5. A method of treating the surface of a mold for casting magnesium,which comprises dusting on the surface of the mold a salt selectedfromthe group consisting of sulfides of antimony and bismuth, minimizingthereby burning of the metal during casting and effecting alloying ofthe surface layers of the casting with the metal of said sulfide toprovide the casting with a protective coating. V 6. A method of treatingthe surface of a mold for casting magnesium, which comprises applying tothe surface of'the mold a suspension of a salt selected from the groupconsisting of sulfides of antimony and bismuth, minimizing therebyburning of the metal during casting and effecting alloying of thesurface layers of the casting with the metal of said sulfide to providethe casting with a protective coating.

7. In a method of preventing excessive burning of magnesium duringcasting and of providing a protective coating on the finished casting bysuperficial alloyin the step of casting magne-. slum in molds havingincorporated therein antimony pentasulflde-in an amount of between 2 andparts by weight for every 100 .parts of the material of the mold.

, 8. A mold for casting magnesium which mold contains a salt selectedfrom the group consisting of sulfides of antimony and bismuth in surfaceexposure, minimizing thereby burning of the magnesium during casting andeffecting alloying of the surface layers of the casting with the metalof said sulfide to provide the casting with a protective coating.

9. In the method of treating material for forming a mold for castingmagnesium, the. step which comprises incorporating in such moldingmaterial a salt selected from the group consisting of sulfides ofantimony and bismuth, minimizing thereby burning of the metal duringcasting and effecting alloying of the surface layers of the casting withthe metal of said sulfide to provide the casting with a protectivecoating.

FRITZ HANSGIRG.

